Separation of aromatic and sulfur compounds



March 21, 1950 A. P. LIEN ET AL SEPARATION OF' AROMATIC AND SULFURvCOMPOUNDS Filed July 2, 1946 WNY y UT.

Patented Mar. 21, 1950 SEPARATION OF ROMATIC AND SULFUR COMPOUNDS ArthurP. Lien, Hammond, Ind., :and Bernard L. Evering, Chicago, Ill., assgnorsto Standard Oil Company, Chicago, Ill., a corporation of IndianaApplication July 2, 1946, vSerial No. 681,121

This invention relates to a process for separately vrecovering aromatichydrocarbons and sulfur compounds from hydrocarbon oils. .Moreparticularly, it relates to a process for treating solutions comprisingaromatic hydrocarbon and sulfur compounds with liquid HF-BF3 mixturesand thereafter recovering separate fractions containing I-IF-BFa,aromatic hydrocarbons and sulfur compounds, respectively.

It is known A.that liquid HF-BFa mixtures are solvents for aromatichydrocarbons and sulfur compounds contained in various hydrocarbonmixtures, for example, in various petroleum fractions Wherein they arefound in admixture with paraiilnic and naphthenic hydrocarbons. Theextraction of vthe aromatic hydrocarbons and s111- fur compounds byliquid HF-BFs may be accompanied by more or less catalytic cracking,isomerization of paraiiin hydrocarbons, alkylation or other reactions,depending on the operating conditions such as temperature, ratio ofhydrocarbon charging stock to the HF-BFa, the concentration of BFS inthe HF, etc. The primary purpose of the process of treating ahydrocarbon mixture containing aromatic hydrocarbons and sulfurcompounds may, in fact, be to eifect a chemical conversion of thehydrocarbon charging stock under the catalytic influence of HF-BFsmixtures, 4and the extraction of aromatic hydrocarbons and sulfurcompounds by liquid HF-BFs mixtures may be incidental Ato saidconversion.

One object of our invention is to provide a process for the separaterecovery of Varomatic hydrocarbons and sulfur compounds from ymaterialscontaining the same, for example, petroleum hydrocarbon mixtures such ascrude oil, lubricating oil fractions, gas oil, gasoline, naphthas andvthe like, or from coal tar fractions. Another object of our inventionis to provide a process for the preferential dissociation ofco-ordination compounds vof aromatic hy'drocarbons-BFx-.HF in therpresence -of .co-.ordination compounds of .sulfur compounds-HF-.BF3- AnAadditional*object of .our invention ris to provide a process lfor theseparation of .boron fluoride from .co-ordination compounds thereof witharomatic hydrocarbons and sulfur compounds. .Further objects of ourinvention will become apparent :from the ensuing description fthereo'f,read :in conjunction with the accompanying schematic-flow diagram.

We have discovered a novel process for the liberation `of aromatichydrocarbons ifi-'om solu tions thereof 'in 'liquid .hydrogeniiiuoride-:boron Afluoride mixtures which lalso .contain .sulfur com- 12Claims. (Cl. 19E-13) pounds. We have alsordiscoveredfa process :for the55 separate recovery of aromatic hydrocarbons and organic sulfurcompounds from solutions thereof in `liquid hydrogen fluoride-boronfluoride mixtures, preferably mixtures containing a minor proportion ofboron uoride betWeenabout 1 and about 40 Weight per cent, based on theweight ofhydrogen fluoride.

Solutions of `aromatic hydrocarbons in .liquid HF-BFs have heretofore'been prepared and it has been proposed to liberate aromatichydrocarbons therefrom by distilling HF .and BFs from said solutions ata .10W temperature, for example, about 19 C., as set forthin ILS.Patentf2,343,84'1 of R. E. Burk. However, .it has `not heretoforebeenappreciated that aromatichydrocarbons and organic sulfur compounds.could be separately regenerated .from their joint solution in -liquidHF-BEs.

.In the interests of .simplifying the nomenclature .used herein, Werefer to solutions of aromatic hydrocarbons .and organic sulfurcompounds in liquid I-IF-BF3, although we appreciate the fact .thatthese are not simple solutions in the ordinary sense vof the term.Rather, it appears that BFs or BFa and HF .unite chemically in theso-called solutions with aromatichydrocarbons and organic sulfurcompounds to produce co-ordination compounds i. e., more or less stable.chemical compounds sometimes known as complexes and theseco-ordinationcompounds are soluble vin 4the HF component of the solution, which ispresent in excess. Free HFis present in the solutions and preferablyalso some free BFS. K

We have discovered that co-ordination compounds of aromatic hydrocarbonswith BF3 and HFcan generally be more readily dissociatedthanco-ordination compounds of organic sulfur com lpounds with BF3 and HF.When the aromatic hydrocarbon co-ordination compounds are heated totemperatures between about 100 F. and about 200 F., preferably .betweenabout 120 F. and about 160 F. appreciable dissociation occurs, resultingin the liberation of free HF and 'BFS on the one hand, and aromatichydrocarbons on the other. In a preferred form of our invention,dissociation of the aromatic hydrocarbon co-ordination compoundsiseffected with simultaneous Vaporization-of HF and BFS and .their removalfrom the dissociationvzone at about the .rate at which they are formed,tending thus to increase .the degree of `completion of .the dissociationreaction. The dissociation of the aromatic hydrocarbon coordinationcompounds can be effected at superatmospheric pressures, le. g.,.between about 5 and .about -100 p. s. i., but it is preferable to .con-

3 duct the dissociation and distillation of HF and BFa at atmosphericpressure or even at subatmospheric pressures between about 0.2 and about10 p. s. i. absolute.

'Ihe removal of HF and BF3 accompanying dissociation of the aromatichydrocarbon co-ordination compounds is also very important for thereason that, as these uorides are removed, free aromatic hydrocarbonsseparate from the solu tion and can be recovered, preferably in a zoneseparate from the dissociation zone by gravity separation methods, e.g., settling, decantation, or centrifuging. Simultaneously, a stratum ofhigher specific gravity than the aromatic hydrocarbons separates fromthe solution which has been substantially denuded of HF and BFs. The

relatively higher specific gravity stratum consists l of co-ordinationcompounds of organic sulfur compounds with BFa and HF and may contain asmall proportion of free HF and BFS.

We have found that the co-ordination compounds of sulfur compoundsreferred to above are more resistant to dissociation than theco-ordination compounds of aromatic hydrocarbons and that a highertemperature is therefore necessary to liberate BFg and HF from saidco-or dination compounds of organic sulfur compounds. Specifically wehave found that temperatures in the general range of about 160 F. toabout 500 F. are necessary to dissociate said co-ordination compounds ofthe organic sulfur compounds, and preferred temperatures are betweenabout 200 F. and about 400 F. The dissociation of the coordinationcompounds of organic sulfur compounds can be effected under asuper-atmospheric pressure, for example, between about 5 and about 100p. s. i., but is preferably conducted at substantially atmosphericpressure or even at subatmospheric pressures, with removal of free HFand BFa from the dissociation zone at substantially the rate at whichthey are evolved. Inert gases may be passed through the zones whereinco-ordination compounds of aromatic hydrocarbons or sulfur compounds arebeing dissociated in order to facilitate stripping of HF and BFs fromsaid zones. Suitable inert gases include carbon dioxide, nitrogen,methane, ethane, propane and the like.

Our process finds its preferred application to light gas oil and lowerboiling hydrocarbon oils. In general, We have found that the lighter thefeed stock, the greater the degree of selectivity of separation ofsulfur compounds and aromatic hy* drocarbons.

In order to illustrate, but not to limit, our invention reference ismade to the accompanying schematic flow diagram which depicts oneembodiment of our process. The charging stock can be any liquidhydrocarbon mixture containing aromatic hydrocarbons and organic sulfurcompounds. The charging stock may be, for example, a petroleum gas oilcontaining aromatic hydrocarbons and organic sulfur compounds, or adistillate or residual lubricating oil fraction. It should preferably bein a substantially anhydrous condition. Predrying of the charging stockcan be effected by conventional processes for drying hydrocarbon oils,as by percolation through a bed of adsorptive alumina or silica gel, ormay be effected by contacting the charging stock with an aqueous HF-BF3mixture, e. g., aqueous HF-BFs produced in the process because of thegradual accumulation of water in the reaction system even when apre-dried charging stock is employed.

It is desirable to reduce the viscosity of viscous charging stocks bydilution thereof with a suitable amount of a light parainic hydrocarbon,e. g., pentane, hexane or a paraflinic gasoline or naphtha fraction. Thelow boiling parafhnic diluents serve not only to reduce the viscosity ofthe charging stock, thereby facilitating contacting operations, but alsoaid in the recovery of HF from the treated charging stock, as will beexplained hereinafter.

The charging stock is introduced from source I0 by pump il through. line52, heater i3 and line lll to a low point in contacting vessel l5.Make-up HF and BFS are introduced into line Il! through line il althougha portion may be introduced through line l E. Generally speaking weprefer to employ liquid HF-BF3 mixtures which are substantiallyanhydrous or which contain only a trace of water, i. e., an amount ofthe order of 0.01 to l weight per cent and in any case not more thanabout 3 weight per cent. 'v'v'e prefer to employ mixtures containingbetween about l and about l0 weight per cent of boron fluoride based onthe weight of hydrogen fluoride, although we may employ solutionswherein the weight of boron fluoride is in excess of the weight ofhydrogen fluoride. In contactor I5, which is preferably provided withsuitable means of agitation (not shown) the hydrocarbon charging stockis treated under controlled conditions of time, pressure, temperatureand ratio of charging stock to HF-BFs. The contacting operation mayinvolve simply the extraction of aromatic hydrocarbons and sulfurcompounds from the charging stock or it may involve chemical conversionof the charging stock as a principal or incidental proc ess, theoperating conditions being suitably adjusted to effect the desiredpurpose.

For example, extraction of aromatic hydrocarbons and organic sulfurcompounds from hydrocarbon fractions containing the same, for ex ample,petroleum or coal tar fractions may be effected at temperatures betweenabout -30 F. and about 200 F., preferably at temperatures between about65 F. and about 85 F. The pressure in contactor l5 is ordinarilyadjusted to maintain the charging stock and a substantial proportion ofthe HF-BFx in the liquid phase. We prefer to employ BF3 in an amountsufficient to exert a positive partial pressure, e. g., 5 to 200 p. s.i. g. The existence of a positive partial pressure of B Fs in thecontacting zone indicates that BFa is present in an amount in excess ofthat which is necessary to combine with aromatic and sulfur compounds inthe charging stock. Between about 5 and about 300 volume per cent of theliquid HF-BFs mixture or even more may be used, based on the volume ofhydrocarbon charging stock although, generally, amounts between about l0and about 100 volume per cent are employed.

A portion of the sulfur compounds in the charging stock can be convertedto HzS by charging hydrogen, also, to contactor l5. A hydrogen partialpressure between about 50 and 3,000 p. s. i. g., preferably about 200 toabout 2,000 p. s. i., may be employed. Increased hydrogenation may beeffected by employing a nickel liner in contactor I5. When hydrogen isemployed, we prefer to use temperatures between about 150 F. and about500 F., preferably about 250 F. to about 400 F.

If a hydrocarbon charging stock such as gas oil containing both aromatichydrocarbons and organic sulfur compounds is to be cracked in contactorl5, temperatures between about F.

and about '400th may befemployed. l Usually a temperature-'of theorderof about 2122.1. is suitable, preferred temperatures ranging betweenabout 180'* F'. and about 300 F. They pressurein the contacting zonewillbe adjusted'to maintain substantially yliquid phase conversionconditions. At a. temperature of about 212 F. ythe pressure may be oftheiorder of400 p. s. i. g. The charging stock 'is caused to -passupwardly through aliquid column of catalyst in the contacting zone at aspace velocity which may be about 1 volume of charging stock per hourper volume of catalyst in the reactor, although space velocities betweenabout 0.2 and about-4 may be used. The cra-cking catalyst comprisesliquid HF-BFa mixtureswhich may contain between about 1 and about 40 percent by weight of BFa based on'the HF.

It should be understood that the ratio of catalyst to charging stock inthe cracking process mayvary depending upon the Atype of charging stockYAand the operating conditions which it is desired `to employ incontacting zone l5. Generally speaking larger amounts of catalyst arerequired .with charging stocks of more refractory character, ire.,stocks more decient in hydrogen and richer in aromatic hydrocarbons, andlesser amounts of catalystare required with relatively clean or morehighly parainic charging stocks.

The weight ratio of hydrocarbon to catalyst introduced into the reactormay thus vary from about :1 to 1:2.

Contacting-maybe effected in any suitable type of contactor von abatchwise, multiple batch, semi-continuous or continuous basis but weprefer to employ a continuous process with a tower type contactor and topass the charging stock upwardly through a column of the liquid I-IF-BFsmixture with or without mechanical agitation. We may use concurrent orcountercurrent contacting. The contactor may be of the type described inUps. Letters Patent'No. 2,238,802 and No.'2,349,821. It may be'about 5to 50 feet high and should be designed to withstand a maximum operatingpressure which, with high temperatures-may -be as much as 1000 p. s. i.g. or more. Beforecontacting is initiated the contactor may be filledabout 1/2 to full of the liquid HFLBFS and its temperature may beadjusted as desired byconventional means. The bulk of the fluoride ysolution separates from the eiuent product stream in the upper part ofthe contactor although some of the :fluoride solution is carried withthe eluent product stream through line I9 and cooler` to separator 2 l.Fluoride material K whichsettles 'out' in this settler-or separator canberreturne'd by lines 23 "and 24 to contactor I5, a `pump 22 beinglemployed Awhen separator 2| is loperated at a vpressure below thereactor pressure or if the settler is not elevated sufciently to insuregravity return.

Boron fluoride together with a small amount of 'fixed gases which may beproduced can be vented from the top of separator 2| through line 25 andpassed through line 26 which leads to the base of absorber 21. Theremaining liquid product'stream'flows over'weir 28 and passes by line 29to BFa stripper 30 which is provided with a suitable reheating means orreboiler 3| at its base. Line 29 may be providedwith a suitable pressurereducing valve or pump depending upon therelative pressuresfinseparator2| and stripper 3Ilrespectively VThe stripper vmay operate at arpressure 'of'about 200 -or 300 prs. i., for example insure the removalof substantiallyall of the BF; which passesby line 32compressor 33 (ifneces-. sary), and line 2S to the base of absorber 21. Make-,up BFa canbe supplied from source 34 and introduced into the contacting system bycompressor 35 to line 26.

.After vremoval of BFs, the product stream passes `byline 36 toazeotropic distillation still 31 which is provided with a suitablereheating means or reboiler 31 at its base and which may be providedwith reflux means at its top. In the azeotropic still the HF isdistilled with a. light parain hydrocarbon such as propane, butane,pentane, etc. which may have been introduced with the charging stock toserve also as a Viscosity-reducing diluent, or may be introduced intothe still from source 4| and valved line 42r through settler d3, line t6and reilux pump 41. In the operation of the azeotropic still, abutane-HF azeotrope, -for example, passes overhead through line 38,condenser 39 and lines 4U and 42 to settler 43, which is operated at aslow a temperature as can be obtained with available cooling water,preferably well below 100 F. The condensed azeotrope separatesv into aheavier HF stratum which is withdrawn by line 44 to HF storage tank 45.The upper butane stratum is returned by line 00 and pump 41 to still 31and may eventually leave the still with the product stream through line49. Light gases may be vented from settler 43 through valved line 48;such gases should contain no BFs, but if they do, they can be introducedthrough line 2B to absorber 21.

The product stream is .withdrawn from the base of the azeotropic still31 through line 49. The product stream is usually substantially freefrom organic iiuorides and hence may require no special treatment fortheir removal. Conventional bauxite or equivalent treating system l ispreferably employed at this point, however, to remove any traces ofiluorides which may be present. The product stream leaves the fluorideremoval zone by line 5| and may, if desired, be subjected to furthernishing treatments as may, in the specic case, be required or desirable,such as fractional distillation, washing, contacting with activeabsorbent clay or the like.

It should be understood that we are not re stricted to azeotropicdistillation for the purpose of removing HF from the products. Ordinaryor flash distillation may be used for this purpose.

A solution of BFS, aromatic hydrocarbons and sulfur compounds inliquid-HE' is withdrawn from contacter l5 through line 512 or fromsettler 2| through lines 23 and 53 and passed through pressure reducingvalve 5d to a recovery drum 55 which is preferably operated nearatmospheric pressure, for example, at about 5 to about 50 lbs. gaugepressure and at a temperature between about and about 200 F., preferablybetween about and about 160 F. Under these conditions cri-ordinationcompounds of aromatic hydrocarbons and BFa are dissociated and free HFand BF3 are vaporized and passed overhead through line 50. This mixedeiiluent may pass directly through condenser 51 to receiver 58, where HFis collected as a liquid and from which BFS -may be flashed overheadthrough line di) to line i8. Liquid HF may be pumped from receiver 5Sthrough line 50 and pump 0| to HF storage tank- 45, provided with avalved vent line 4'5". There is a tendency for moisture to Vaccumulatein the system even when substantially dry charging stocks are employedbecause of .the

extremely hygroscopic nature of HF and BFa; to remove moisture fromthese luorides it is desirable, from time to time, to introduce theeffluent rom line 56 through valved line 62 into distillation column 63provided with heating means 64. In distillation column 63, substantiallyanhydrous HF and BFa are vaporized and pass overhead through line 65 andcondenser` 51 to receiver 58. A portion of the condensate in receiver 58is returned through line 66 to serve as reflux in distillation column63. Aqueous HF-BFg may be withdrawn from the base of column E3 throughline 61 and treated by known methods for the recovery of the fluoridecomponents. A portion of the aqueous HF-BFB may be used to pre-dry thecharging stock to the process.

l Heating of the materials in drum 55 results in dissociation of theBF2-HF aromatic hydrocarbon co-ordination compounds or complexes anddistillation of HF and BFS, whereby the aromatic hydrocarbons are thrownout of solution. The residue in drum 55, comprising aromatichydrocarbons and sulfur compound co-ordination compounds, is withdrawnthrough line 63 to settler 69 wherein an upper stratum of aromatichydrocarbons is formed and can be recovered from the lower stratum ofsulfur-containing coordination compounds and is removed by line 'Ill forsuch further treatment as may be required or desirable, e. g., washingwith water or alkaline solutions such as ammonia, contacting withadsorbent clays or bauxite and fractional distillation into fractions ofdesired boiling range. The

aromatic hydrocarbons recovered by the process of our invention may beused in the preparation of high solvency naphthas or valuable materialsfor organic synthesis.

The complex material which settles out in settler 69 is withdrawnthrough valved line 1| to recovery drum l2 which is provided withheating means 13. This drum is operated, preferably at about atmosphericpressure, although higher pressures of the order of about 5 to about 50lbs.

per square inch may be used, and at temperatures between about 160 F.and 500 F., preferably between about 250 F. and about 350 F. Under theseconditions co-ordination compounds of BFa-HF-sulfur compounds aredissociated and free HF and BFs are vaporized and passed overheadthrough line I8, compressor 'M and line I8 into absorber 21 or throughline M into contactor l5. It is preferably to pass the effluents of lineI8 to absorber 21, this arrangement offering the advantages of providingbetter control of the amount and composition of the HF-BFS mixtureentering contactor I5 and the possible elimination of compressor 14.

A concentrate of organic sulfur compounds is withdrawn from drum 'l2through line 'l5 and may be subjected to such finishing treatments asare required or desirable, e. g., washing with ammonia or aqueousallralies, fractional distillation and the like. The organic sulfurcompounds can be adapted to various uses such as manufacture of extremepressure agents for lubricating oils and greases, oxidation to sulionicacids or other organic syntheses.

Further purification and concentration of the aromatic hydrocarbons andsulfur compounds withdrawn respectively through lines 'lll and 15 can beeffected by subjecting them, separately, to repeated extraction withliquid HF-BFs mixtures containing, preferably, between about 1 and about40 weight per cent of BFs based on the HF.

These treating operations may be effected in contactors of the type ofcontacter I5; the apparatus used for re-treating may, in fact,essentially du plicate the contacting, settling and fractionationequipment described for use in the main treating operation. There-treating operations may be carried to a suiiicient length to obtainessentially pure aromatic hydrocarbons free from organic sulfurcompounds and organic sulfur compounds substantially free of aromatichydrocarbons.

In our studies of the desulfurization of hydrocarbon oils containingaromatic hydrocarbons and organic sulfur compounds, we have observedthat BFa or liquid HF-BFc mixtures extract appreciable quantities ofsulfur compounds before the extraction of aromatic hydrocarbons isinitiated. The extraction of aromatic hydrocarbons from the feed stockbegins only after variable proportions of the organic sulfur compoundshave been extracted, depending on the boiling range of the chargingstock. For example, in the extraction of 750 cc. of furnace oil fromSlaughter crude oil, containing 1.46 weight per cent of sulfur in theform of organic sulfur compounds in sequence with a solvent consistingof l() grams of liquid HF and with 34 grams of RFB-10 grams of HF for1/2 hour at 70-74" F. under a pressure of 25 p. s. i. g., we haveobserved that "I2 weight per cent of the sulfur was removed but thatthis degree of sulfur removal was accompanied by only a slight change inrefractive index (from nD2 of 1.4771 to 1.4680) and specic dispersion(from 129 to 124) indicating that substantially no aromatic hydrocarbonshad been extracted from the feed stock. However', above this level ofsulfur compound extraction, aro matic hydrocarbons were being extractedin rapidly increasing quantity as evidenced by a rapid drop in thespecific dispersion of the refined oil.

We have also extracted a heavy naphtha containing 0.39 weight per centof sulfur in the form of organic sulfur compounds with 50 cc. of HF and10 grams of BFs per liter of naphtha for one hour at about F., followedby a gravity separation of a hydrogen fluoride solution (extract phase)and a lower specific gravity stratum refined naphtha or raflinatephase). It was observed in this experiment that although 94 weight percent of the sulfur was extracted from the naphtha, the specificdispersion of the naphtha remained unchanged at a value of 116,indicating that no aromatic hydrocarbons were extracted from thenaphtha. However,` under conditions leading to more thoroughgoingextraction of the organic sulfur compounds from the naphtha we havefound that aromatic hydrocarbons are simultaneously extracted with theorganic sulfur compounds.

It is thus possible, by careful control of the quantity of HF-BFs toextract substantially all the organic sulfur compounds from solutionswith aromatic hydrocarbons, preferably by multiple batch extractions.

We have also observed that liquid, substantially anhydrous HF exhibitsdifferent solvent properties from BF3 solutions in .liquid HF. Whereasliquid HF-BF3 mixtures exhibit a pronounced capacity to dissolve andextract aromatic hydrocarbons of the most diverse types, e. g., monoorpolynuclear aromatics and benzenoid- (e. g., phenanthrene) or quinonoidtype (e. g., anthracene) aromatic hydrocarbons, liquid HF alone is muchmore selective in its action and extr cts little or no mononucleararomatic hydrocarbons or benzenoid type polynuclear aromatichydrocarbons while exhibiting a marked solvent power towardsquinonoid-type' poly-- nuclear aromatic hydrocarbons such as anthracene.However, liquid. HF, like BFS solutions in liquid HF, is a good solventfor organic sulfur compounds.

We have noted that hydrocarbon charging stocks containing organic sulfurcompoundscan be practically desulurized by treating with HF vapor. Thesulfur compounds and some polynuclear aromatic hydrocarbons in thecharging stock react with some of theHF forming a complex which isinsoluble in the oil and the complex can be gravity separated as aliquid along with dissolved HF.

Thus, it is possible to treat mixtures of organic sulfur compounds andaromatic hydrocarbone of the type which are not markedly sol'- uble inliquid HTF with liquid HF in an amount sulicient to extract asubstantial proportion of the sulfur compounds, preferably by multiplebatch extraction, in order to obtain sulfur-free aromatic hydrocarbonson the one hand and organic sulfur compounds substantially free ofaromatic hydrocarbons on the other.

Make-up HF can be added to the system from source 'iii to storage tankd5. Hydrogen iluoride is pumped from this storage tank by pump 'il .s

and passed by line lt to the upper part of absorber 2l which may beoperated at a pressure between about 50 and about 400 p. s i. or higher,e. g., about 250 p. s. i. At such pressures and at a relatively lowtemperature of the order of about 100 F. the BFS is absorbed in the HFbut hydrocarbon gases are not absorbed therein and may be vented fromthe top of the absorber through valved line l5. By this means losses ofBFS are substantially prevented iwhile the system is being purged ofmethane or other light gases which may tend to accumulate in the systemas the result of cracking or other reactions. It should be understoodthat make-up HF `can be introduced directly into the top of the absorberand that line Sil and/or 50 may likewise lead to the absorber ratherthan to an HF storage tank.

Our invention is not limited to the use oi HF as an absorbent for BFSsince any other selective absorbent liquid may be employed. An intimateliquid mixture or solution of HF and an aromatic hydrocarbon(particularly an alkyl aromatic hydrocarbon containing I to il carbonatoms per molecule) is particularly advantageous because BFS reacts wi isuch mixture to form a complex which is soluble in liquid HF. Thus, wemay introduce such alkyl aromatics (for example a portion of thearomatic hydrocarbons from line 10) into the upper part of .the absorberthrough line 80' and we may obtain an intimate mixture of such aromaticsand l-IF'either by the manner in which these liquids are introduced intothe absorber tower or by the use of mechanical means. Any BFS which isnot absorbed in the HF in the lower part of the absorber will thus bechemically combined with the HF-aromatic mixture at the top of theabsorber so that practically no BFS will leave the top of the tower withextraneous gases even when the absorber is operated at pressures as lowas atmospheric pressures. By this method of operation we may avoid thenecessity of employing compressors 33 and it and like-- Wise avoid thenecessity of operating drum l2 at the higher temperatures and pressureswhich would be required for the introduction of liberated HFaud BFSintov a high pressure absorber.v

When liquid HF alone is used to absorb the BFS, the resulting solutionis passed into contactor t5 through valved line il and line I4. Whenappreciable quantities of aromatic hydrocarbons are employed in absorber2i to aid in the absorption oi BFs, it is preferable to pass all or asubstantial proportion of the resulting solution through line ilandvalved line 8 l ,thence through pressure reducing valve 54 into recoverydrum 55 in order to separate aromatic hydrocarbons from the iiuoridecomponents prior to the introduction of. the latter into contactor I5.

Although in referring to the accompanying schematic Aflow diagram wehave described a process wherein HF and BFS are used together, it shouldbe understood that our invention is not thus limited. Although aromaticswhose nor.- mal boiling points are below 600 F. are not appreciablysoluble at ambient` temperatures in liquid hydrogen uoridesome of thearomatics having boiling points above 600 F. are appreciably soluble atambient temperatures in liquid hydrogen fluoride. Thus in the case of acharging stockV thaty contains HF-soluble high boiling aromatics, it ispossible, if desired, to take advantage of the peculiar solvent powersof liquid, substantially anhydrous` HF. Using HF alone as the lsolventit is not possible, however, to separately recover aromatic hydrocarbonsand sulfur cornpounds from their solution in the hydrogen uoride.However, HF alone could be used in the operation of contactor i5following which a hydrogen fluoride extract. phasel withdrawn throughktheir different thermal stabilities, as pointed out above. Converselythe charging stock can rst be contacted with BFa alone in contactor I5,following which a BFS-containing phase is witndrawn through. line 52 andcan be treated in a separate zone (not shown) with liquid HF to producea solution which is passed into recovery drum 55 in order tor instituteoperations for the recovery of the components of the solution.

The following examples are adduced in order to illustrate, but notunduly to limit, the results obtainable by the process of our invention.

EXAMPLE I In order to demonstrate the effect of BFS-HF mixture as adesulfurizing agent, a sampley or" Mid-Continent virgin gas oilcontaining 0.12 per cent sulfur was treated in two steps (A and B) asshown in the following table:

Upon completion of step A, a 445 g. sample of raiinate was withdrawnvfor analysis, following which 414 additional grams of charging stockwere added to the remaining reactor contents together with 47 grams ofBFs. Contacting in both steps was effected in a 1570 cc. carbon steelbomb fitted with a 1725 R, P. M. stirrer and a bleed-olf tubeterminating at a point well above the liquid level of the liquid HFsolution, allowing ready removal of supernatant raffinate. Uponcompletion of the second step, the rainate and HF phases were separatedby settling and were treated as pointed out below.

It was noted that the amount of BFs required to give a positive pressureon the reactor in these runs was several times that required forordinary parainic charging stocks. This observation, coupled with thefact that in the two runs a total of 85 grams of BFS remained bound inthe catalyst phase, indicates the formation of BF?. complexes. The factthat only 2.5 grams of BF; would be consumed by reacting mol for molwith the sulfur present indicates the formation of a BFs-aromatichydrocarbon complex; this is further borne out by the analysis shownbelow, as well as discussed more fully hereinafter.

The catalyst layer (HF phase) (611 g.) from the above runs was subjectedto dissociative distillation at 190 F. to remove HFBF3. comparativelylow temperature, 68 g. of BFs distilled and were collected, indicatingthat the BFS- aromatic complex, is a rather loosely-held additioncompound. Most of the HF originally added to the reactor also distilledover at temperatures below 190 F., along with some organic material.Upon removal of a substantial proportion of the free HF and BFS bydistillation, the catalyst layer separated upon standing into asupernatant aromatic hydrocarbon stratum and a lower stratum comprisingprincipally co-ordination compounds of BFa-HF-organic sulfur compounds.

The following tabulation presents a comparison of the charging stock andthe products produced in each step.

The hydrocarbon product (rainate) from the above runs was water-white ascompared to the straw-colored feed. As shown in the above table thesulfur content was reduced to zero indicating that the HF-BFs medium isa very eiiicient agent for extraction of sulfur from hydrocarbons,either at or 120 F. The process appears to take place through theformation of an addition complex between sulfur compounds and BFa,followed by solution of this complex in the liquid HF phase.

Of considerable interest is the fact that substantial quantities ofaromatics have been removed from the original gas oil and that theresultant product is highly parainic as shown by specific dispersions,refractive indices and specic gravities. Corresponding to disappearanceof aromatics from the upper hydrocarbon phase is the fact that thecatalyst phase increased substantially in volume and that thehydrocarbon obtained from the catalyst layer in the manner describedbelow is very highly, if not completely, aromatic as shown by thephysical properties listed in the above table.

The residue remaining after dissociation of At this 12aromatic-co-ordination compounds and distillation of excess HF and BFsconsisted of two distinct layers. The upper layer, light in color,proved to be highly aromatic as previously mentioned. The bottom layerwas quite dark and viscous, apparently consisting of an organicallybound BFa-sulfur compound complex. Heating this complex to 358 F.resulted in the liberation of 10 g. BFs, which, together with the 68 g.recovered on the original heating at F., gives a total recovery of 78 g.as compared to the 85 g. which disappeared into the catalyst during thetwo runs (the remainder of BFs was bled out with the gases leaving thereactor).

EXAMPLE II A transformer distillate from Winkler crude oil, whichdistillate contained 1.54 per cent sulfur, was treated in sequence at 50F. with varying amounts of BFa as shown in the following table. The samereactor was used as in Example I.

Treatment of Winkler transformer distillate with H F-BFs Conditions C DIn run C just enough BFs was added to provide one mol of BF: per mol ofsulfur in the feed. The 21 g. of BF: thus added was completely absorbed,leaving no pressure on the reactor and liberating no BFa on bleeding outthe product. As shown in the following table the raffinate (product)retained a substantial amount of sulfur as well as aromatics, thecontent of the latter being indicated by specific dispersion, refractiveindex and specific gravity. Upon completion of run C, a 426 g. sample ofrainate was withdrawn for analysis and an additional 448 g. ofdistillate and 91 g. of BFs were added to the reactor to carry out runD.

In'run D, an excess of BFS was used, i. e., sufficient to give apositive pressure of 65 p. s. i. on the reactor contents when stirred at50 F. Of the 91 g. of BFa added, only 25 g. were recovered on bleedingout the product. As shown in the table, the sulfur compound removal wasgood and most of the aromatics were extracted to give a substantiallyparamnic-naphtnenic rainate.

Approximately 300 g. of the 1088 g, of hydrocarbon treated in the tworuns went into solution in the liquid HF layer. The sulfur content ofthis layer was 5.6 weight per cent. On heating this layer to 190 F. HFdistilled o. After distillation of the material boiling up to 190 F.,the residue separated by gravity into two layers. The upper layer wastransparent and, as shown by the data in the table, consistedsubstantially of aromatic hydrocarbons. The bottom layer was a blackcomplex which was hydrolyzed with aqueous am- -monia (on heating) togive a product with the properties listed in the last column of thefollowing table:

1 Boiling Range, 637708 F.

It will be noted that, in both examples, the aro-, matic layer obtainedcontains about the same amount of sulfur as the charging stock butmarkedly less sulfur than that of the total extract or of the separatedsulfur layer.

Having thus described our invention whatwe claim is:

1. Thev process of regenerating aromatic hydrocarbonsl from a solutionof aromatic hydrocarbons and sulfur compounds in liquid HF-BFa, saidsolution comprising co-ordination compounds of BFs and I-IF .witharomatic hydrocarbons and organic sulfur compounds, which processcomprises subjecting said solution to a dissociative distillationoperation at a temperature between about 100 F. and about 200 F.,separating a distillate comprising HF and BF3 from said distillationoperation, separating a distillation residue comprising free aromatichydrocarbons and HF-BFs co-ordination compounds of organic sulfurcompounds, subjecting said residue to gravity separation, and separatelyrecovering an aromatic hydrocarbon fraction and a fraction comprisingco-ordination compounds of organic sulfur compounds.

2. A process of treating -a solution of aromatic hydrocarbons and sulfurcompounds in liquid HF-BFa, which process comprises subjecting saidsolution to dissociative distillation at a temperature between about 100F. and about 200 F., recovering a distillate comprising HF land BF3,separating a distillation residue comprising aromatic hydrocarbons andco-ordination compounds of BFs-HF-organic sulfur compounds, subjectingsaid residue to gravity separation and separately recovering an aromatichydrocarbon fraction and a fraction comprising co-ordination compoundsof organic sulfur compounds, and subjecting the last named fraction todissociative distillation at a temperature between about 160 F. andabout 500 F.

3. A hydrocarbon treating process which comprises contacting ahydrocarbon charging stool: containing aromatic hydrocarbons and organicsulfur compounds with liquid HF containing BFS under conditions adaptedto form a solution of aromatic hydrocarbons and sulfur compounds in saidliquid HF, subjecting said solution to dissociative distillation at atemperature between about 100 F. and about 200 F. and recovering as adistillate fraction a substantial proportion of I-IF and BFS thereincontained, recovering a residue from said distillation and subjectingthe same to gravity separation, separately recovering an aromatichydrocarbon fr-action and a fraction of higher specific gravitycomprising coordination compounds of BFa-HF-organic sulfur compoundsfrom said gravity separation, and recycling at least a portion of saiddistillate fraction to said hydrocarbon treating process.

4. A hydrocarbon treating process which comprises contacting ahydrocarbon charging stock containing aromatic hydrocarbons and organicsulfur compounds with liquid HF containing BF3 under conditions adaptedto form a solution of aromatic hydrocarbons and sulfur compounds in saidliquid HF, subjecting said solution to disso- -ciative distillation at atemperature between about 100 F. and about 200 F. and recovering as adistillate fraction a substantial proportion of HF and BF3 thereincontained, recovering a residue from said distillation and subjectingthe same to gravity separation, separately recovering an aromatichydrocarbon fraction and a fraction of higher specific gravitycomprising co-ordination compounds of Blb-HF-organic sulfur compoundsfrom said gravity separation, subjecting said fraction of higherspecific gravity to dissociative distillation at a temperature betweenabout 160 F. and about 500 F. and. separately recovering HF-BFg andorganic sulfur compounds, and recycling at least a portion of the HF andBFS derived from said dissociative distillation operations to saidhydrocarbon treating process.

5. A hydrocarbon treating process which comprises contacting ahydrocarbon charging stock containing components boiling above about 600F. and containing organic sulfur compounds and aromatic hydrocarbonswith liquid HF under conditions adapted to form a solution of aromatichydrocarbons and organic sulfur compounds in said liquid HF, contactingsaid solution with BFs to produce a second solution, subjecting saidsecond solution to a dissociative distillation operation at atemperature between about F. and about 200 F., separating a distillatecomprising HF and BFz from said distillation operation, separating adistillation residue comprising free aromatic hydrocarbons andco-ordination compounds of organic sulfur compounds, subjecting saidresidue to gravity separation, and separately recovering an aromatichydrocarbon fraction and a fraction comprising co-ordination compoundsof organic sulfur compounds, subjecting the last named fraction tothermal dissociation at a temperature between about 160 F. and about 500F. and separating a fraction comprising HF-BF3 and a fraction comprisingorganic sulfur compounds.

6. The process of claim 5 wherein the charging stock is a gas oilcontaining organic sulfur compounds and aromatic hydrocarbons.

7. The process of claim 5 wherein the charging stock is a lubricatingoil containing organic sulfur compounds and aromatic hydrocarbons.

8. The process of claim 4 wherein hydrocarbon treating is effected undersubstantially noncracking conditions.

9. The process of claim 5 wherein the hydrocarbon treating is effectedunder substantially non-cracking conditions.

10. The process of claim 2 where the first named dissociativedistillation is eiectedat a temperature between about F. and about F.and wherein the last named dissociative distillation step is carried outat a temperature between about 200 F. and about 400 F.

11. The process of claim 4 wherein the iirst named dissociativedistillation step is carried out at a temperature between about 120 F.and about 160 F. and wherein the last named dissociative distillationstep is carried out at a temperature between about 200 F. and about 400F.

12. A hydrocarbon treating process which comprises contacting ahydrocarbon charging stock containing components boiling above about 600F. and containing organic sulfur compounds and aromatic hydrocarbonswith liquid HF under conditions adapted to form a solution of aromatichydrocarbons and organic sulfur compounds in said liquid HF, contactingsaid solution with BFa to produce a second solution, subjecting saidsecond solution to a dissociative distillation operation at atemperature between about 100 F. and about 200 F., separating adistillate comprising HF and BF3 from said distillation operation,separating a distillation residue comprising free aromatic hydrocarbonsand co-ordination compounds of organic sulfur compounds, subjecting 75said residue to gravity separation, and separately recovering anaromatic hydrocarbon fraction and a fraction comprising (zo-ordinationcompounds file of this patent:

UNITED STATES Pii'riaxizfrs of organic sulfur compounds. Number NameDate ARTHUR p, LIEN, 2,343,841 Burk Mar. 7, 1944 BERNARD L. EVERING. 52,375,675 MatuSZak May 8, 1945 2,378,762 Frey June 19, 1945 REFERENCESCITED 2,405,995 Burk Aug. 20, 1946 d 2,408,173 Matuszak Sept. 24, 1946The iollowm,D refei ences aie of leoora 1n the 2,427,009 Lien et alSept' g, 1947

1. THE PROCESS OF REGENERATING AROMATIC HYDROCARBONS FROM A SOLUTION OFAROMATIC HYDROCARBONS AND SULFUR COMPOUNDS IN LIQUID HF-BF3, SAIDSOLUTION COMPRISING CO-ORDINATION COMPOUNDS OF BF3 AND HF WITH AROMATICHYDROCARBONS AND ORGANIC SULFUR COMPOUNDS WHICH PROCESS COMPRISESSUBJECTING SAID SOLUTION AT A DISSOCIATIVE DISTILLATION OPERATION AT ATEMPERATURE BETWEEN ABOUT 100*F. AND ABOUT 200*F., SEPARATING ADISTILLATE COMPRISING HF AND BF3 FROM SAID DISTILLATION OPERATION,SEPARATING A DISTILLATION RESIDUE COMPRISING FREE AROMATIC HYDROCARBONS